FunctionalUnit is the class of units that includes inflectional and derivational units. Functional units attach to roots and stems and can be used to form morphological paradigms in a grammatical description.

The relation hasConstituent is an abstract partial ordering relation that expresses dominance between two linguistic units. This relation is meant to cover all possible types of linguistic constituency: phonological, morphological, syntactic, etc. constituency.

The relation hasMorphologicalConstituent is an abstract partial ordering relation that expresses dominance between two morphological units. This relation is meant to cover all possible types of morphological constituency.